1. Technical Field of the Invention
The present invention relates generally to the field of optical spectrum analyzers; and more particularly, to an optical spectrum analyzer apparatus that includes an optical tapped delay line (OTDL) unit for separating input light into component wavelengths, and to a method for analyzing the spectral content of a light signal.
2. Description of Related Art
An optical tapped delay line (OTDL) is a passive optical device that can be used to convert a single optical beam into a plurality of identical, spatially distinct beams at uniform time delays. An important characteristic of an OTDL is the capability of presenting a long optical path within a small space and to permit a controlled tapping off of energy from an optical beam at uniform intervals to provide the plurality of spatially distinct beams.
OTDLs have been used in optical communications systems, such as Wavelength Division Multiplexing (WDM) or Dense Wavelength Division Multiplexing (DWDM) systems, to increase the transmission capacity of the systems. In particular, by modulating each of the plurality of spatially distinct beams formed by the OTDL with a different information signal, and then recombining the modulated beams, the plurality of information signals can be simultaneously transmitted through a single optical fiber or other wave guiding device of the optical communications system.
It is also known to utilize a virtually imaged phase array (VIPA) in optical communications systems. A VIPA is a device that is capable of receiving input light focused on a front surface thereof and having a wavelength within a continuous range of wavelengths, and producing output light that is spatially distinguishable in accordance with the wavelength of the input light. VIPA devices have been used in optical communications systems to compensate for chromatic dispersion, as a wavelength demultiplexer and in other applications.
In order to ensure the proper design and operation of an optical communications system such as a WDM system, it is necessary to analyze the spectral content of light signals transmitted through a wave guiding device of the system. This is typically accomplished using an optical spectrum analyzer (OSA). Ever improving optical communications systems, however, require an optical spectrum analyzer that has a spectral resolution higher than that provided by conventional optical spectrum analyzers.
There is, accordingly, a need for an optical spectrum analyzer apparatus having improved spectral resolution for use in optical communications systems and in other applications.